VXT6 KRK speaker, schematic/advice please

[zen]

Hi all

This one has no power

Anyone worked on this model?

[zen]

Re: VXT6 KRK speaker, schematic/advice please

Protection relay not clicking over to release AC supply to bridge rectifier

[zen]

Re: VXT6 KRK speaker, schematic/advice please

First casualties

R65 & R66, both 2R2 0.25W O/C

[zen]

Re: VXT6 KRK speaker, schematic/advice please

Well, nothing else found to be faulty.

Caps checked out good, & manufacturer hasn't even used excessive amounts of glue that I'm used to seeing on monitor speakers.

Uprated wattage of resistors, as they may have been slightly underrated.

Working on test.

[maxeringade]

Re: VXT6 KRK speaker, schematic/advice please

First casualties

R65 & R66, both 2R2 0.25W O/C

Hi!

I know its an old thread but i have a VXT8 i bought used with these exact two resistors, R65 & R66, missing... someone replaced them with wires.

Do you know what are their roles in the circuit? i could not find the schematics and i was wondering if it is safe to run the monitor like this. It works, but it does not seems right....

[CapLeaker]

Re: VXT6 KRK speaker, schematic/advice please

Used as a fuse and probably were flame proof too.

[maxeringade]

Re: VXT6 KRK speaker, schematic/advice please

Used as a fuse and probably were flame proof too.

i attached two pictures, one of the monitor that is missing components and other of the untouched monitor, as you can see, 2 diodes (D10 & D11) are also missing. Are them supposed to act as fuses too?

[CapLeaker]

Re: VXT6 KRK speaker, schematic/advice please

Either something is disabled, or got modified somehow. The diodes rectify AC to DC. I guess you have to see where these traces go.

[maxeringade]

Re: VXT6 KRK speaker, schematic/advice please

Either something is disabled, or got modified somehow. The diodes rectify AC to DC. I guess you have to see where these traces go.

Yes, you guessed right. Theres a mod, it is hardwired to 230V, the switch is disconnected and it only works on 230 volts. Image attached.


The only modifications on the circuit are the two resistors bypassed and the two diodes removed.

Does the missing components correlates with the hard wired 230v only mod?

thanks

[slerner]

Re: VXT6 KRK speaker, schematic/advice please

I'm presently trying to fix a VXT6, one of a pair I bought new & worked just fine until I had to put them away during a 3 month remodeling project. In other words, they'd been powered-up on standby almost continuously since 2007. When I plugged them back in, they sounded right. Except some crackling started coming from one unit. Barely noticeable in the background of the audio signal, at first. As I tried different audio cables & sources, I noticed the crackling continued even with no audio cable plugged in. So I resumed using it and hoped it would magically improve. Within about an hour, I heard a ominous pop and the music stopped. The back plate (which barely ever got warm in my heaviest use) was almost too hot to touch! I unplugged the power. After several hours, I got brave & opened the case. The two largest caps looked puffy. I removed them and they tested completely dead. So I replaced them, but the unit still wouldn't power up. I managed to find OEM replacement boards at a reasonable price, so I ordered a pair. Straight out of the factory packaging, they were both dead. Well, one did power up for a second, then its caps popped. The other board did nothing at all.
I'm presuming that on all 3 boards, the caps dried out from prolonged disuse. [sound plausible??] The replacement boards had been warehoused in Malta (hot) since KRK discontinued the VXT6 10+ years ago. And all the caps are TWBOR 105º, black with white writing. Can't find any relevant datasheets online or any corresponding series in their catalog.
Is replacing the electrolytic caps the next thing to do? Does anyone have a data sheet? If not, should I match the capacitance, meet/exceed the temp & voltage?